R help - Feb 2010 - help with EXPASY HTML form submission in RCurl package

Hi,

I am trying to submit a form to the EXPASY protscale server (
http://www.expasy.ch/tools/protscale.html). I am using the RCurl package and
the postForm function available in it. I have extracted the variables for
the form from the HTML source page. According to the syntax of postForm, I
just need to mention the url and assign values to the input mentioned in the
HTML code.
The code that I am using is:
postForm("http://www.expasy.ch/tools/protscale.html",
    "sequence" = "
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
    scale = "Molecular weight",
    window = "5",
    weight_edges = "100",
    weight_var = "linear",
    norm = "no",
    submit = "Submit"), .checkparams = TRUE)
the constant error that I get is:
Error in postForm("http://www.expasy.ch/tools/protscale.html", .params
list(sequence = "not",  :  STRING_ELT() can only be applied to a
'character
vector', not a 'logical'

Is there any other way to submit an HTML form in R ?

Thanks for the help

Regards

Sunando

	[[alternative HTML version deleted]]

Sunando Roy wrote:
> Hi,
> 
> I am trying to submit a form to the EXPASY protscale server (
> http://www.expasy.ch/tools/protscale.html). I am using the RCurl package
and
> the postForm function available in it. I have extracted the variables for
> the form from the HTML source page. According to the syntax of postForm, I
> just need to mention the url and assign values to the input mentioned in
the
> HTML code.
> The code that I am using is:
> postForm("http://www.expasy.ch/tools/protscale.html",
>     "sequence" = "
> AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
>     scale = "Molecular weight",
>     window = "5",
>     weight_edges = "100",
>     weight_var = "linear",
>     norm = "no",
>     submit = "Submit"), .checkparams = TRUE)

I don't think that is what you actually submitted to R.
It is a syntax error as you end the cal to postForm) after "Submit"
and then have an extra  ", .checkparams = TRUE)" afterwards.

But, when you remove the ')' after  "Submit",
the problem you get is that .checkparams is not a parameter
of postForm(), but .checkParams is.  R is case-sensitive
so the problem is that .checkparams is being treated as a parameter
of your form.

So change the p to P in .checkparams, and it works.

  D.
> the constant error that I get is:
> Error in postForm("http://www.expasy.ch/tools/protscale.html",
.params > list(sequence = "not",  :  STRING_ELT() can only be
applied to a 'character
> vector', not a 'logical'
> 
> Is there any other way to submit an HTML form in R ?
> 
> Thanks for the help
> 
> Regards
> 
> Sunando
> 
> 	[[alternative HTML version deleted]]
> 
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.